Regression of metastatic carcinoid tumors with octreotide therapy: two case reports and a review of the literature

BACKGROUND: The antiproliferative effect of the somatostatin analogue, octreotide, on metastatic carcinoid tumors is poorly understood. Partial tumor regression seen radiographically has been reported with the use of octreotide therapy for neuroendocrine tumors. Complete regression of carcinoid tumors is rarely reported. RESULTS: Two patients with metastatic midgut carcinoid tumors were treated with subcutaneous octreotide 300 microg/day for symptomatic control of their carcinoid syndrome before debulking palliative surgery. During the laporatomies, both patients were found to have complete macroscopic regression of the metastatic lesions that had been identified radiologically before surgery, including liver metastases in one patient and periportal and retrocaval lymph nodes in the other. After surgery, the patients were evaluated every 3 months, and had no detectable disease at 30 and 43 months, respectively. Thirty cases of partial tumor regression with octreotide administered with or without other treatment modalities have been reported in the literature. Most of the patients involved received other treatment modalities. Only one other case reported in the literature showed complete regression with octreotide monotherapy. CONCLUSIONS: We report two cases of metastatic midgut carcinoid tumors that demonstrated a significant anti-proliferative response to octreotide monotherapy. Review of the literature failed to identify any specific prognostic factors with which the response to octreotide can be predicted. Possible mechanisms for this antiproliferative effect of octreotide on carcinoid tumors are discussed.